An Interesting Cause of Wide Complex Tachycardia: Ashman’s Phenomenon in Atrial Fibrillation

BackgroundAshman’s phenomenon is an aberrant intraventricular conduction abnormality that occurs in response to a change in QRS cycle length. In atrial fibrillation, Ashman’s phenomenon will present as a long RR cycle followed by a short RR cycle, with the subsequent QRS complex manifesting a right bundle branch block morphology. This morphologic variation can create difficulty with electrocardiographic interpretation, and can alter management in patients with this dysrhythmia.ObjectivesThis report presents a case, describes the Ashman’s phenomenon in atrial fibrillation, and discusses interpretation of this electrocardiographic finding.Case ReportThis is a 27-year-old woman who presented with palpitations and chest pain. The patient was symptomatic with a heart rate >200 beats/min and a wide complex tachycardia on electrocardiogram.ConclusionsAshman’s phenomenon should be suspected in atrial fibrillation when there is a long cycle followed by a short cycle, with the subsequent QRS complex manifesting a right bundle branch block pattern. Emergency physician awareness of this phenomenon may improve diagnostic certainty and have an impact on dysrhythmia management.